Control system



Jan. 6, 1948. v H. B. HOLTHOUSE, JR v ,8

CONTROL SYSTEM Filed Nov. 2, 1942 s'sheets-sneet 1 Q N l P Q Q I CONTROL SYSTEM 3 Sheets-Sheet 2 Filed Nov. 2, 1942 Jan. 6, 1948. B. HOLTI-OUSE, JR 2,433,845

CONTROL SYSTEM Filed Nov. 2, 1942 3 Sheets-Sheet 3 Patented Jan. 6, 1948 CONTROL SYSTEM 7 V I Harry B. Holthouse, IL, Chicago, 111., assignor to Motorola, Inc., a corporation of Illinois Application November 2, 1942, serial No.464,2"70

4 Claims. (01. 219-39) This invention relates generally to control systems and in particular to a control system for starting and operating an electrically operated heating system of combustion type.

Electrically operated heating systems generally include a resistance means of some kind for preparing and/or igniting a combustible mixture for burning. In these systems, and particularly those in which the supply of electrical energy for the resistance means is Variable, many difficulties are encountered in starting combustion of the mixture. Where the source of electrical supply for the heating system is a battery, the effective capacity of which varies between a high and low charge condition of the battery, these difficulties are further increased with the operation of the heating system at cold temperatures because of thereduction in the effective capacity of the battery with cold temperatures. Thus a control system capable of satisfactorily operating a battery-operated heating system at relatively warm temperatures and with a normal charge on the battery, may be completely ineffective to operate the heating system at temperatures of F. and less due to the reduced effective capacity of the battery and the increased heat demand required'of the resistance means to operate at an optimum temperature at cold temperatures. Many efforts have been made to overcome these difficulties but so far they have been unsuccessful.

It is an object of this invention therefore, to provide a control system for a battery-operated heater of combustion type which is adapted to positively start the heater under cold temperature conditions.

Yet another object of this invention is to provide a control system for a heater of combustion type having a battery as the sole source of power supply, which is capable of positively operating the heating system over a, wide range of variations in the effective capacity of the battery.

A further object of this invention is to provide a control system for a heater apparatus having a battery as the only source of power and resistor means for heating a combustible mixture to initiate combustion, which is adapted to vary the application of the battery energy on the resistor means so that it will operate to heat the mixture to an optimum temperature for all charged conditions of the battery.

A feature of this invention is found in the provision of a control system for a batteryoperated heater of combustion type havingresistor means for heating a combustible mixture to an optimum temperature to initiate combustion, in which second resistor means series connected with the heating resistor is "adapted to be cut out of'the operating circuit of the heating resistor to'boost the supply of battery energy to the heating resistor when the energy supplied to the heating resistor through the second resistor is insufficient to operate the heating resistor to heat the combustible mixture to an optimum temperature;

Yet another feature of this invention is found in the provision of a control system for a battery-operated heater apparatus having a resistor l or heating a combustible mixture to an optimum temperature to initiate combustion, in which resistance means associated. with the operating circuit of the heating resistor is arranged between the'battery and the heating resistor to control the application of the battery energy on the heating resistor such that it may be operated to'heat the combustiblemixture to an optimum temperature for wide variations in the efiective capacity of the battery.

Further objects, features and advantages of this invention will become apparent from the following description when taken in connection with the accompanying drawings in which:

Fig. 1 is" a longitudinal sectional view of a heater apparatus adapted to be operated by the control system of this invention, showing the combustion'portion of the heater apparatus in development;

Fig.2 is a transverse sectional view of the combustion portion of the heater apparatus as seen along the line 2-2 in Fig. 1;

Fig. 3 is a longitudinal sectional view showing in 'detaila fuel conditioning unit for the heater apparatus;

Fig; 4 is a'diagramm'atic control circuit showing one embodimentof the control system of this invention;

Fig. 5 is adiagram'matic' control circuit showinga modified form ofthe inventionpand Fig.6 is adiagrammatic control circuit showingyet another modification of the invention.

This invention isillustrated in the drawings as applied; to a battery-operated heater of internal combpstiontype having a combustion portion andanair andfuel mixing or conditioning portionconnected with the combustion portion to prepare a combustible mixture for burning in the combustion portion. The mixing portion includes 'a combination heating and igniting unit having' a heatingcoil which heats the fuel to at least a fuel vaporizing temperature for mixing with the air in the conditioning portion, and then ignites the vaporous air and fuel mixture for burning in the combustion portion. In order to quickly and positively start a burning of the mixture in the combustion portion it is necessary that the heating coil be operated to heat the fuel in as short a time as possible to thoroughly vaporize the fuel for mixing with the air. Any delay in the initial preparing of the combustible mixture, or a failure of the heating coil to heat the fuel to at least a vaporizing temperature, of course will prevent an immediate starting of the heater or any starting at all. The heat generated by the coil is dependent upon its resistance characteristics and the amount of energy applied on the coil from the battery. Thus a battery having a normal pressure of twenty-four volts might vary from a high charge condition of thirty volts to a low charge condition of about eighteen volts. A coil constructed to operate at twenty-four volts might thus operate satisfactorily between twenty-four volts and thirty volts but at eighteen volts would not operate at all, or would take considerable time in reaching an optimum temperature to prepare the fuel for burning. A coil capable of being heated to substantially a maximum temperature at eighteen volts would operate at an overload above this voltage and would burn up when thirty volts were applied to it. These difiiculties are overcome in the present invention by the provision of a control system which includes the heating coil and resistance means for varying the energy applied to the heating coil from the battery. Since the energy or effective capacity of the battery varies with its charged condition and with temperature conditions, the coil is constructed to operate with a maximum heat output at the lowest charged condition of the battery, with the resistance means at normal and high charge conditions of the battery being connected with the heating coil so that only a part of the battery charge is applied on the heating coil. On starting of the heater the energy applied to the heating coil is reduced by the resistance means. Should this energy be insufiicient to operate the heating coil at an optimum temperature for heating and igniting the air and fuel supplied to the conditioning portion, the resistance means is cut out of the operating circuit for the heating coil so that all of the battery energy is applied to the coil to boost its heat output. It is to be understood, of course, that even though the battery might be at a normal voltage its efiective capacity may be reduced with cold temperatures to a value such that it may be necessary to apply the full voltage of the battery on the heating coil at cold temperatures. As a result, a normal operation of the heating coil is provided over a wide variation in the values of the efifective capacity of the battery so as to assure a positive and quick starting of the heater.

Referring to Fig. 1 the heater apparatus to which the control system of this invention is applied is shown as including a housing II] which is divided longitudinally over substantially its entire length by a vertically extending partition member I I into a mechanical compartment I2 and a heating compartment 13. Within the heating compartment is a substantially cylindrically shaped combustion chamber I4, shown in development in Fig. 1 for the purpose of clarity, which is closed at one end by a cover plate I6 and at its opposite end by the bottom I! of a substantially cup-shaped member I8. The cup member I8 defines in part an air supply chamber I9 which ber I9.

4 is in axial alignment with the combustion chamber I4.

The combustion chamber I4 is longitudinally divided into four axially extending but connected passages 2la-2Id by a partition member 22 of substantially X-shape (Figs. 1 and 2). The combustion chamber inlet 23 and outlet 24 are in the bottom portion ll of the cup-shaped member I8 and in communication with the passages 2Ia and 2| d, respectively. Located within the inlet 23 is an air and fuel mixing means, indicated generally as 25, which will be later fully explained. The outlet 24 is connected with a tail pipe assembly 26 extended outwardly from the housing I0 through the air supply chamber I9.

The outer wall or body portion of the combustion chamber I4 (Fig. 2) is integrally formed with alternately arranged peripheral portions 21 and doubled fin portions 28 which are angularly spaced about the combustion chamber and extended axially thereof. Side portions of the partition member 22 are located within the inner open ends of certain ones of the fins 28 and held in a fixed position relative to the combustion chamber body portion. The fins 28 have a sleeve 23 positioned about their outer closed ends to form an annular passage 3| about the combustion chamber [4 for air to be heated.

The air to be heated enters the housing l0 through an inlet 32 opening into the mechanical compartment I2 and is moved by a fan 33 into a chamber 34 connected with the air passage 3|. The fan 33 is mounted on the shaft 35 of a motor 30, with both the fan 33 and the motor being located in the mechanical compartment I2. The air from the passage 3| is discharged through an outlet 36 connected with the space to be heated. The compartment I2 and the air chamber 34 are separated from the air supply chamber 19 by a partition member 31 positioned transversely of the housing In and about the open end of the cup-shaped member I8. The member I8 cooperates with the partition member 31 and housing end structure 20 to define the air supply cham- Air to the air supply chamber I9 is supplied by a fan 38 mounted on the motor shaft 35 which is journaled in the partition plate 31. An inlet 39a to the fan 38 is provided in the housing end structure 20. The fans 33 and 38 are thus concurrently operated by the motor 39.

The motor 39 also operates a fuel pump 39 which is of a solenoid type. It is to be understood, of course, that any electrically operated pump may be used. A breaker assembly 4| is associated with the motor shaft 35 to control the energization of the pump 39 which is connected to a suitable source (not shown) by a pipe 42 and delivers fuel through a pipe 43 to a fuel injection nozzle 44 mounted on the air and fuel mixing means 25.

The air and fuel mixing means 25 includes a tubular shaped housing member 46 having a substantially closed end portion 41 located in the air supply chamber l9 and an open end portion 48 extended within the combustion passage 2Ia (Figs. 1 and 3). A mixing chamber 49 located in the closed end 47 is separated from an equalizing chamber 5i by a perforated heat conducting plate 52. The equalizing chamber 5I in turn is separated from the combustion chamber passage 2Ia by a perforated heat insulating plate 53. Positioned axially of the casing 46 and through the chambers 49 and SI is a combination heating and igniting unit 54 including a resistance coil 56 supported in a spaced relation within a heat conducting tube 51 of copper or like material. The casing 45 and the partition plate 52 are also composed of a heat conducting material, such as copper or the like, and are in thermal connection with the combination unit 54 so as to be readily heated thereby. The combination unit 54 operates to heat the air and fuel mixing means 25 to at least a fuel vaporizing temperature to vaporize the fuel supplied thereto by the pump 39 for mixing together with the combustion air supplied by the blower 33, and to ignite such mixture for burning in the combustion chamber l4. The fuel nozzle 44 is connected with the mixing chamber 49 and is located within the air supply chamber iii. A portion of the air from the air chamber i5) enters the nozzle 44 through ports 55 and travels through the nozzle into the mixing chamber 49. Further air is admitted directl into the mixing chamber 49 from the air supply chamber 19 through apertures 58 arranged about the mounting for the fuel injection nozzle 44. The fuel entering the mixing chamber is heated to at least a fuel vaporizing temperature by the heat generated by the combination unit 54 and is intimately mixed with the air in such chamber, the heat from the heating unit being readily transferred to the casing "85 and plate 52 which are thermally connected with the combination unit 54. This mixing is made more thorough and complete by the turbulence of the air in the mixing chamber. The mixture passes into the equalizing chamber 5! through the apertured plate 52, the equalizing chamber, in conjunction with the insulating plate 53 and a screen structure 65 extended across the perforations in the plate 53, functioning to retard the mixture flow through the conditioning means 25 to reduce the turbulence of the mixture and disperse the same substantiall uniformally across the entire open end 48 of the casing 46. A vaporous mixture of substantially uniform fuel characteristics is thus provided at the outlet 48 for ignition by the combination unit 54 which functions as a heat gun. In other words the heat developed by the coil 55 is projected outwardly from the copper tube 51 with the heat generated being dependent upon the watt input to the resistance coil 55, Ignition of the total mixture may be initiated by the prior ignition of a portion thereof which is admitted from the equalizing chamber 5| to a point adjacent the open end of the tube 5'! through a tube 59. The vaporous mixture, after ignition, is burned in the combustion chamber M, the exhaust gases being discharged through the exhaust pipe assembly 26. The blower 38 operates to maintain an air pressur in the air chamber 19 on the order of about two inches of water. Since this pressure alone acts on the combustion chamber burning takes place in the combustion chamber at substantially atmospheric pressure.

, It is thus readily apparent from the above description that a quick starting and efiicient operation of the heater apparatus is dependent upon a positive operation of the coil 56 to heat the conditioning portion or means 25 to at least a fuel vaporizing temperature. It follows also that the sooner the coil can be operated at an optimum temperature, the less delay there will be in starting the operation of the heater.

Since the conditioning portion 25 is extended within the combustion passage 2| a and is thermally connected with the combustion chamber M at the combustion chamber inlet 23, the heat of combustion radiated and conducted to the conditioning portion 25 maybe sufficient after initial heater'operatio'n to retain the same at fuel vaporizing temperature, and at least aids the further air and fuel supplied for burning the greatest difficulties in the operation of the heater apparatus are encountered during its starting period.

Where a large amount of electrical energy is available for operating the heater air and fuel supply portions, as well as the igniting means, it is a relatively simple matter to provide a coil which will be capableof generating sufficient heat to vaporize the fuel inthe conditioning portion 25 regardless of the temperature conditions under which the heater is operated. However, where a battery is utilized as the sole source of power supply for the heater the electrical energy for operating the heater is limited entirely by the avail able effective capacity of the battery, The effective capacity varies over relatively wide limits defined by a low and high charge condition of the battery. Further variation takes place because of the reduction in the effective capacity with cold temperatures. It is recognized, of course, that batteries vary in size, weight and rating to permit their application to many uses. These considerations of space and weight are particularly important where the heater apparatus is to be used for space or engine heating in airplanes, and particularly in pursuit and bomber planes. The batteries normally used in bomber and pursuit ships have a pressure of twenty-four volts and are rated at about 1'7 ampere-hours. It may happen, furthermore, that the charging service on these batteries, during their normal use, is rather infrequent, so that the charge of the battery must be utilized to the fullest extent. The

power conditions for operating a heater apparae tus for aircraft heating are thus very critical, and the power demands on the battery must be reduced to a minimum while concurrently providing for a positive and quick starting of the heater apparatus as well as an efficient operation after starting under very rigorous operating conditions.

With reference to Fig. 4 there is shown a control system of this invention adapted to operate a plurality of the heaters shown in Fig. 1 from a single twenty-four volt battery rated at 17 ampere-hours. Five heaters are illustrated as exemplary of the usual number of heaters required in the heating of the cabin and engines of a four engine bomber or pursuit ship. Each heater includes a similar control circuit indicated generally as 61, only one of which is shown in detail. The battery and heaters, as well as the electrical connections between the battery and heaters must all be of a minimum weight for carrying in the plane. In one embodiment the complete heater unit shown in Fig. 1 has a weight of about eighteen pounds. Weight considerations as to the cable connection between the heaters and the battery requires the use of a relatively light cable 62. In one embodiment this cable is about three hundred feet long and to reduce its weight as much as possible it is made of #14 wire. Although the use of a #14 wire appreciably reduces the weight of the cable it also increases the resistance of the overall control system and in turn the power demand on the battery 65. Because of the emergency conditions under which the heaters in bomber and pursuit ships must operate a quick starting of the heater is essential under all weather and temperature conditions.

Since in some localities temperatureson the order H and the heating coil 55.

7 of -40 F. to 50 F. might be encountered a rugged and positive operating control circuit is absolutely necessary.

In Fig, 4 a control circuit 6| for a heater, from the battery 66, includes the cable lead 62 which is connected to a double-throw double-pole switch 63 having corresponding pairs of terminals 64 and 66, and 6'! and 68. The switch 63 in a position for starting the operation of the heater completes the circuit for the heating coil 56 from the conductor cable 62 through a switch arm 63, terminal 66, a resistor H, a conductor 12, the heating coil 56 and a ground connection 13. The motor circuit is also closed at starting and includes from the cable 62 the switch arm 14, terminal 66, conductor 16, the motor 36 and a ground connection TI. The motor 30 and the heating coil 56 are thus concurrently operated when the switch 63 is in its start position, the circuit for the pump 39 being open. In order to provide for a heating of the coil 56 to a temperature sufiicient to vaporize the fuel admitted into the conditioning or mixing means 25, regardless of the charged condition of the battery 60 and under cold temperature conditions, it is of a construction adapted to be operated when the charge on the battery is reduced to eighteen volts. The resistor 1 I, series connected with the heating coil, has resistance characteristics providing for a six volt drop. This resistance, of course, can be Varied to any amount depending upon the normal operating voltage of the coil 56. With the battery 66 at a normal pressure of twenty-four volts and with the switch 63 in its start position only eighteen volts are applied on the heating coil 56 which at this voltage has normal operation. With the battery in a high charge condition, of course, the coil 56 will operate at an overload. However, this overload is not sufficient to seriously injure the coil.

The switch 63 is manually actuated and after it has been held in a start position by the operator of the heater apparatus for a length of time to preheat the conditioning means 25 to at least a fuel vaporing temperature, it is thrown from its start position to the run position indicated in Fig. 4. During the short time interval required in moving the switch 63 from a start to a run position the circuits for the heating coil 56 and motor 30 are open. To eliminate any cooling of the coil 56 during this time, the operator, simultaneously with the moving of the switch 63 closes a switch 18 connected by conductor 19 to the cable 62 and by conductor 8| to the conductor I2 intermediate the resistor The circuit for the switch 18 is thus a shunt circuit for the resistor II. On closing of the switch 76, therefore, substantially the full energy of the battery 66 is applied through this shunt circuit to the heating coil 56. Thus instead of a momentary cooling of the heating coil 56, when the switch 63 is moved from a start position to a run position there is provided a boost or increase in the energy applied on the coil and in turn an increase in its heat output. On closing of the switch 63 in its run position the circuit for the motor is completed from cable 52 through switch arm 14, terminal 6T, conductor 82, and terminal 64, the rest of the circuit from the terminal 64 being the same as when the switch 63 is in a start position. The circuit for the pump 39 is closed from the cable 62 through switch arm 69, terminal 68, the pump 39, breaker assembly 4 I, and a ground connection 83. If, after the pump 39 is operated,

combustion takes place in. the combustion chamber H, as will be indicated to the operator by the exhaust gases being discharged from the tail pipe assembly 26 or by the sound of the burning mixture in the combustion chamber, the switch 18 is released to open the circuit of the heating coil 56, the circuit for the motor 30 and the pump 39 remaining closed through the main control switch 63. If, however, combustion does not take place on the admission of fuel into the conditioning means 25 the momentary switch 18 is held closed till combustion has started. Because closing of the temporary switch 18 shorts the resistor H from the circuit of the heating coil 56 the full energy of the battery 60 is applied on the heating coil 56 to boost its heat output. Thus even though some free fuel might be in the mixing chamber 49 of the conditioning means 25, as a result of the low heating of the conditioning means by the initial operation of the coil 56, the boost in the heat output of the coil acts to quickly vaporize this free fuel as well as the fuel introduced into the mixing chamber by the continued operation of the pump 39.

Where the efiective capacity of the battery 60 is known to the operator to be of a low value, the switch 18 may be closed during the time the switch 63 is at its start position so as to assure a positive operation of the coil 56 to heat the mixing means 25 to a fuel vaporizing temperature. This method of operation thus provides for a pre-heating of the conditioning por tion by an initial full application of the battery energy on the heating coil with this full energy being applied until after combustion has been started. Under extreme cold temperatures and low battery conditions the switch 16 is initially closed, while switch 63 is open to eliminate the cooling effect of the cold air from blower 38 from action on the conditioning unit 25. When the conditioning unit is heated to a fuel vaporizing temperature the control switch 63 is moved to a run position while the temporary switch 18 is held closed. When combustion starts the switch I8 is released.

To stop the operation of the heater it is only necessary to open the switch 63. However, to assure a complete burning of all of the residual fuel in the conditioning unit 45 and combustion chamber l4 the switch from a run position is initially moved to its start position to operate only the motor 30 and the coil 56. After the residual fuel is burned the switch 63 is opened. The combustion chamber and conditioning unit are thus swept clean of all free and residual fuel to facilitate later starting of the heater. Each of the control circuits in Fig. 4 is operated in a similar manner to that described above to start the operation of a corresponding heater.

In the operation of the heater units in Fig. 4 it may sometimes happen that, after combustion has been started and notwithstanding the fact that the conditioning portion 25 is thermally connected with the combustion portion l4, combustion may be lost in a heater due to a cooling down of the conditioning portion 25 to a temperature below that capable of vaporizin the fuel admitted to the mixing chamber 49. When this occurs the attendant or operator regains combustion in the lost heater by operation of its corresponding control circuit in the manner above fully explained. This manual operation of a control circuit to regain combustion, rather than the provision of automatic means to close the operatin circuit for the heating coil 56 when with the ground through a conductor 93. metal arm 94, in the thermostatic switch 84, is

i the temperature of the condition means 25 falls below a certain value, is necessary because of the rigorous power demands on the battery 60. In army installations, as well as in some commercial installations, an attendant is always near so that this manual control is no handicap. Because of the plurality of units in operation at the same time it is entirely possible that, with automatic means used to operate the heating coil in response to the combustion conditions in a corre-' the heaters would be out and the attendant would be without any specific indication as to the reason for heater failure and as a result would have to check the entire installation before attempting to restart the heaters. However, with a manual control the operator immediately knows which heater has lost combustion. If any of the remaining heaters should go out while he is working on the one which has lost combustion this fact is immediately known to him so that he will have no trouble in making the necessary checks and then operating the control circuits to restart the heaters which have gone out. Thus because of the extreme conditions mentioned both as to the power supply and the temperature conditions under which the heaters must be positively operated there is no advantage obtained from automatic operation and in fact such operation under these conditions would not be practical.

In the modified form of the invention in Fig. a control circuit for a single heater apparatus is illustrated havin means for automatically cutting in the heating coil 56 in response to combustion conditions in the combustion chamber Hi. In this modification, the power demands on the battery 66 are less critical than in the embodiment of Fig. 4 so that automatic operation can be used advantageously in maintaining operation of the heater and thus appreciably reduce the attention required by the heater duringits normal operation. Since the circuits in Figs. 4 and 5 are similar in many respects like reference numbers will be used to designate corresponding parts in these two figures.

The circuits for the motor 36, the heating coil 56 and the pump 39 and the control of their operation by the double-throw switch 63 is similar in all respects to the like circuits in Fig. 4 so that a further description of these circuits and their relative control in the starting and running operation of the heater is believed to be unnecessary. The provision of means for automatically cutting in the heating coil 56, on a failure of combustion in the combustion portion It, includes a thermostatic switch unit 85 located in a heat exchange relation with the combustion chamber I 4 as shown in Fig. 1. The unit 64 includes two normally closed contact arms 86 and 8'! which are connected across the terminals 66 and 66 by conductors 88 and 89, respectively. A third contact arm 85 is normally open relative to the contact arm 86 and is connected by a conductor 9! in series with a light 92, which in turn is connected A bil0 engageable with the contact arm 86 and is movable in response to the heat in the combustion chamber 14 to move the contact arm 86 away from the contact 81 and into substantial concurrent engagement with the contact arm 85.

On initial closing of the switch 63 to a start position the circuit of the heating coil is closed from the terminal 66 through the resistor 1 I, conductor i2, heating coil 56 and the ground connection 13. Although the circuit for the heating coil fro-m the terminal 64 is also closed through the thermostatic switch 84, this switch is without any function in controlling the operation of the heating coil 56 on heater starting. After a pre-heating of the conditioning means 25 by the operation of the heating coil 56 with only a part of the electrical energy of the battery 66 applied thereon, the switch 63 is moved to its run position to close the circuits of the motor 36 and pump 56 in all respects similar to the same circuits described above in connection with Fig. 4.

The circuit for the heating coil 56 from the battery lead or cable 62 is closed through the switch arm M, terminal 6'1, conductor 82, terminal 66, the resistor H, conductor 12, the heating coil 56 and the ground connection 13. With the heating coil 56 connected in series with the resistor ll for both the start and run positions of the switch 63 heating of the conditioning means 25 is accomplished by the use of only a part of the battery energy. Should the coil 56 fail to heat the conditioning means 25 to at least a fuel vaporizing temperature so that combustion does not occur when the fuel pump 69 is operated the temporary switch 18 is closed to shunt the resistor ll and apply substantially the full energy of the battery 66 on the heating coil. Switch 18 is held closed until combustion starts. It is ap parent, of course, thatwhen the heating coil 56 is unable to heat the fuel in the conditioning portion 25 to at least a fuel vaporizing temperature that free fuel might accumulate in the conditioning portion 25 tending to produce a flooded condition therein. By virtue of the closing of the momentary switch 16 there is an immediate boost in the energy supply to the heating coil 56, and in turn in its heat output, so that this free fuel as well as the fuel continuing to be introduced in the mixing chamber 49 by the operation of the pump 39 are all vaporized for burning. When combustion is started as the result of the increase in battery energyapplied on the coil 56 the temporary switch 16 is released.

However, since the thermostatic switch 54 is responsive in operation to the combustion conditions in the combustion chamber I 4 the coil 56 after release of the switch 18 may continue to operate in series with the resistor l I. This operabustion has been started and normal operation of the heater accomplished. The pilot lamp circuit I from the terminal 61 includes the conductor 82,

terminal 64, conductor 88, contact arms 86 and 85, conductor 9!, the lamp 92 and the ground connection 53. On a cooling of the combustion portion it below a predetermined temperature value corresponding to substantially a fuel vaporizing temperature for the conditioning means 25,

the. bimetal 94 is cooled. and movestothe left, as viewed in- Fig. 5; topermitthe contact arm 86 to open the pilot 1amp* circuit and to. close the heating coil circuit through the resistor II. A going out of the light 92, therefore,.in'dicates to the operator a loss of combustion and the energization of the coil 56 by only a part of the battery energy, the portion of the battery energy to be applied on the coil 56 being determinedby the resistance characteristics of the resistor 11.

When the effective capacity of the battery is relatively high sufiicient heat will-bedeveloped by the coil 56 to heat the conditioning mean 25 to an optimum temperature so that combustion will automatically be regained. However, if. after a period of operation of theheating coil with a reduced battery supply the light 92 does not go on, a low battery condition is indicated to-the operator, who then presses thetemporary switch 18 to boost the supply of battery energy to the coil 56 to substantially the full energy of the battery. The controlsystemin Fig.5 thus provides anautomatic operation ofthe heating coil during normal heater operation, means for visually indicating normal heater operation,.and-. a boosting circuit for the heating coil through which substantially the full energy of the battery may be applied to the heating coil-to assure its being operated for maximum: heat output. The thermostatic switch means 8t is. ineffective to control the operation ofthe coil 56-w-hen the switch 63-is in a start positionand-hasa control function only when the switch 63- is-in a run position. A positive circuit for starting the heating coilis thus completed onclosing of the switch-63.

In the modified form of the invention shown in Fig.v 6 a thermostatic switch unit 95 is arranged in the control-system to controltheoperation. of the heating coil 56 for both the start and run positions of the switch 63.. When the switch 63 is in a-start position the circuitof the motor 30 from the terminal includes conductor 16, the motor 30 and the ground connection 11. The circuit for the coil 56 from the terminal 64 includes conductor 96,.resistor H, conductor. 91, thermostatic switch 95, conductor 98-,theheating coil 56 and the groun'dconnection'wl Although a second circuit for the coil. 56- is closedfrom'the resistor 'II through conductor 99,- a light 92 and conductor IllI tothe conductor 98,.this circuit is inoperative to energize the heating coil 56because of the negligible current flow in the conductor I! permitted by the lamp 92. Iflhoweventhethermostatic switch unit. 95 isretained openfor some reason, such as ice formations between thecontacts I04 and I06 of the switch. 95, the coil 56 will not operate and the lamp 92 will. light to indicate this condition,the. coil-.56 at this time remaining cool and functioning merely as aground in. the light circuit.

On moving. the switch 61 to its runi position the circuit for the heatingcoil5fi' from theterminal 6! includes conductor I00, resistor II, conductor 91, thermostatic switch. 95,,conductor 96, the heating coil 56, and the ground connection 13. The motor circuitfrom the terminal 61. includes conductors I00 and.9.6,.terminal- 64, conductor 16, the motor 30, andlthe groundconnection 11. The'pump. circuit. from the. terminal 68 includes the pump 39; the breaker assembly. 4|, and the ground connection 83. If'on admission of fuel to the conditioning means 25 combustion does not start in the combustion chamber I4, the temporary switch I8. isclosedtokick upor boost the heat output of. the coil. 56 by shunting the re- 12 sistor H through a circuit which includes from the battery lead 62' the conductor I02, switch 18, and the conductor I03 whichis connected to the conductor 91. This shunting of the resistor II provides for the application of the full battery energy on the coil 56. By virtue of the thermostatic switch 95 being. in the coil operating circuit at all times the switch 18 may be held closed until the bimetal contact I04 and the contact I06, of the thermostatic switch 95, are opened inresponse. to thecombustion conditions in the combustion chamber I4; the thermostatic switch. 95 being carried on the combustion chamber similarly to theswitch 84 shown in Fig. 1. On opening of the. thermostatic-switch 95 the temporary switch I8 is ineffective to control the operation of the heating coil-56.. When the thermostatic switch 95- opens sufiicient current flows through the lamp 92 to lightit and indicate a normal operation of the heater. Although the light circuit, is completed through the coil 56, practically no currentflows throug-hthe coil because of the current limiting action of the-lamp 92. Thecontrol system in Fig. 6 thus provides for o a positive operation of the heating coil to a desired' temperature for a widerange of Values in the efiective capacity of the battery, and for a controlled operation of the heating coil-by thermostatic switch means both during the starting and the normal operation: of the heater appar atus.

From a consideration of the above description it is seen that. the invention provides a control system capable of providing for apositive starting of a battery-operated heater apparatus including a coil for. heating a combustible mixture to a predetermined.temperature-for burning in a combustion portion. The controlsystem may be used in the operation of a single or a plurality of heater units and operates eflioiently to start the heaters for critical power demands on the battery and under temperature conditions as low as -40 F. and F. The completecontrol system is comprisedof aminimum number of parts so that it can be completely checked as to its workability in only a matter of seconds. Provisions in the control system for eihciently and safely operating a heating coilcapableof producing a normal heat output at the lowest voltage at which the battery is to operate, assures theuse of the battery energy to its fullest extent. This is particularly important. in. those installations where battery charging. facilities are not available, and where charging of the operating battery takes place at infrequent periods. A control systemof. this inventionnot-only provides for an eflicient and positive starting of a heater apparatus under. very rigorous operating conditions, but also when the. power demandon the. battery is not criticalor thetemperature operating conditions' too extreme. Thus. it. is. readily apparent that where a full charge can be maintained on the battery the step in the control system of operating the temporary switch I0 may be entire- 1y eliminatedsince sufficient heatwill always be generated by the heating. coil 56 for fuel vaporizing purposes when it is in seriesrconnection with the resistor'll.

Although the invention has been described specifically with. reference to a battery-operated heater using a coil for heating a combustible miX- turev to initiate combustion, it-

to be understood that this system may be applied to any battery-operated systemrequiring a booster circult for. an. element therein. It is. to be understood also that although several preferred embodiments of the invention have been particularly described that it is not to be so limited since alterations and modifications can be made therein which are within the full intended scope of this invention as defined by the appended claims.

I claim:

1. In an electrically operated internal combustion heating system adapted for outdoor operation at low temperatures and having a battery as a sole source of electrical energy and wherein the voltage of said battery is reduced at low temperatures and is also variable within limits de fined by the condition of the battery charge; a heating element for preheating fuel for said heating system and producing ignition thereof operated by said battery, a control system for the heating system having a start position wherein said heating element is operable to preheat the fuel prior to entrance into the combustion chamber and a run position wherein said heating element is operable to preheat the fuel prior to entrance into the combustion chamber and also to ignite the fuel in the combustion chamber, said control system Comprising a, main switch and an auxiliary switch, said main switch being arranged to select said start position or said run position and being adapted to apply only a portion of said battery voltage to said heating element, said auxiliary switch being arranged to apply the full battery voltage to said heating element to provide for operation of the heater When said portion of said battery voltage is inadequate to provide the heat required for satisfactory operation of said heating system.

2. In a control system for electrically operated heating apparatus which is adapted to be operated from a battery of variable voltage and includes means defining a combustion chamber, air moving means provided with an electric driving motor and operable to deliver combustion air to said chamber, a fuel feed system including electrical driving means for delivering fuel to said chamber, and electrical heating means for preheating said combustion air and said fuel prior to admission into the combustion chamber and for producing ignition of the fuel within the combustion chamber; the combination which includes a main switch having asta position wherein said air moving means and said electrical heating means are connected to said battery for preheating said combustion chamber prior to entry of fuel therein, and a run position wherein said air moving means, said fuel feed system and said electrical heating means are connected to said battery for providing combustion in said combustion chamber, said main switch being arranged to apply a portion of the available battery voltage to said heating means, and an auxiliary switch arranged to apply full battery voltage to said heating element to provide for operation of the heater where said portion of said battery voltage is inadequate to produce the heat required for preheating the fuel and providing combustion thereof.

3. In a control system for electrically operated heating apparatus which is adapted to be operated from a battery of variable voltage and includes means defining a, combustion chamber, air moving means provided with a driving motor and operable to deliver combustion air to said chamber, a fuel feed system including a pump for delivering fuel to said chamber and electrical driving means therefor, and electrical heating means for preheating said combustion air and said fuel prior to admission into the combustion chamber and for providing ignition of the fuel within the combustion chamber; a combination which includes a main switch having a start position wherein said air moving means and said electrical heating means are connected to said battery for preheating said combustion chamber prior to entry of fuel therein and a run position wherein said air moving means, said fuel feed system and said electrical heating means are operatively connected to said battery for providing combustion in said combustion chamber, said main switch being arranged to apply a portion of the available battery voltage to said heating means, an automatic switch operating in response to the temperature of the combustion chamber for disconnecting said electrical heating means from said battery when said main switch is in said run position, indicating means for indicating the position of said automatic switch, and an auxiliary switch, arranged to apply full battery voltage to said heating element to pro- Vide for operation of said heating apparatus where said portion of said battery voltage is inadequate to produce the heat required for preheating the fuel and providing ignition thereof.

4. In electrically operated internal combustion heating apparatus adapted for operation from a battery having a voltage which is reduced at low temperatures and is also variable within limits defined by the condition of the battery charge; means defining a combustion chamber having an inlet at one end thereof, a fuel conditioning unit disposed at said inlet and provided with a mixing chamber within which fuel and combustion air may be mixed and then introduced into said combustion chamber, electrically driven fuel feeding means for delivering fuel to said mixing chamber, means defining an air pressure chamber at one end of said combustion chamber, enclosing at least a part of said fuel conditioning unit, said fuel conditioning unit having ports therein through which air from said pressure chamber may be admitted to said mixing chamber, electrically driven air moving means for developing an air pressure within said pressure chamber, electrical heating means at least partially disposed within said mixing chamber and operative to heat the fuel and air during the passage through said mixing chamber and to ignite the mixture within said combustion chamber, a control system for said heating apparatus, comprising a main switch having a start position in which said air moving means and said heating means are connected with said battery for heating said mixing chamber and said combustion chamber prior to entry of fuel therein, and a run position wherein said air moving means, said fuel feeding means and said heating means are operatively connected to said battery for producing combustion in said heating apparatus, said main switch being adapted to apply only a portion of said battery voltage to said heating means, an auxiliary thermostatically controlled switch for disconnecting said heating element from said battery when the temperature in said combustion chamber is suificient to produce combustion without the use of said heating element, an indicating device for indicating the position of said thermostatically controlled switch and further indicating when said heating device is not providing sumcient heat to produce ignition within the combustion chamber, and a second auxiliary switch arranged to apply full battery voltage to said heating element to provide for operation of said heater when said portion of said battery voltage is inadequate to provide the heat required for producing combustion.

HARRY B. HOLTHOUSE, JR.

REFERENES CITED The following references are of record in the file of this patent:

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